Process for the manufacture of storage batteries



Nov. 16, 1948. c. D. GALLOWAY PROCESS FOR THE MANUFACTURE OF STORAGEBATTERIES Original Filed June 3,.1944

rm MA CYZIrZaEG j ?atenteol Nov. i16 1948 ssn PROCESS FOR THEMANUFACTURE OF STORAGE BATTERIES Charles D. Galloway, Wyndmoor, Pa.,assignor to The Electric Storage Battery Company, a cor poraticn of NewJersey G Claims. i.

This invention relates to the manufacture of elements for storagebatteries and, more especially, to the method of casting straps on theplate lugs of an assembled storage battery element and has for an objectthe provision of a method of p ying heat to the strap-metal while in themold along a. localized area adjacent the tips of the lugs to efiectlocalized fusing of the strapmetal to the ends of the lugs withoutfusing of the strap-metal to the roots of the lugs.

Another object is to provide a new and improved method for casting thepositive and negative connecting straps to the plates of a group ofpositive and negative plates with interposed separators completelyassembled in their final relative positions, with localized welding ofthe end-portions of the lugs, and to accomplish this without danger ofinjury to the separators and without the possibility of so-calledrun-downs" of molten metal between the plates.

Another object of the invention is to provide improved methods forcasting the connecting straps to the downwardly projecting plate lugs fthe completely assembledelement in such a manner as to avoidcrystallization and weakening of those ortions of the plate lugs whichare relied upon for the mechanical support of the plates while providingfor good and permanent electrical contact between the lugs and thestrap.

Another object of the invention is to provide for carrying out thestrap-casting operation in two steps whereof the first comprises pouringthe molten metal into the strap mold around the plate lugs of theinverted element at a temperature sufilcient to fill the mold and thespaces between the lugs but insufficient to melt the metal of the lugs,while the second step comprises subjecting the under surface of thestrap-casting as it rests in the mold together with the tips of theplate lugs to an elevated temperature for such brief period of time aswill effect a welding of the lug to the strap for a short distancebeneath said surface without melting or softening or otherwise impairingthe molecular structure of the balance of the lug.

In carrying out the invention in one form thereof molten metal which isnot hot enough to fuse the surfaces of the plate lugs is poured into themold in quantity sufficient to form the strap. While the strap is stillin the mold, heat is applied to a localized area of the mold adjacentthe tips of the lugs to effect localized fusing or welding of thestrap-metal to the end-portions of the lugs without fusing of thestrap-metal to the roots of the lugs. The fused or welded areas are ofhigh electrical conductivity and :provide low resistance paths for flowof current while the shrinkage of the metal about the roots of the lugsupon cooling provides Strong mechanical support of lug roots which havenot been weakened by fusing or crystallization thereof.

The invention will be more clearly understood by referring to oneembodiment thereof described below in connection with the accompanyingdrawing in which:

Fig. 1 is a plan view of a strap-casting mold embodying features of theinvention; and

Fig. 2 is a sectional elevation on the line 2-2 of Fig. 1 showing also aportion of the inverted element.

In the drawing, l0 represents the mold block of any suitable materialsuch as cast iron. It is provided with open top shallow mold cavities Hand 12 of suitable shape and dimensions for casting the desiredconnecting straps, As shown in Fig, 2, the assembled element comprisingpositive plates 83, negative plates l4 and interposed separators |5, islocated in an inverted position with the plate lugs l6 and I1 projectingdownwardly into the corresponding mold cavities II and I2. The elementmay be held together by any suitable clamping device (not shown). Theelement is supported vertically on a slab l8 of heatinsulating andheat-resisting material whose upper surface is slightly above the uppersurface of the mold proper. of the separators I5 rest on this slab andare thus prevented from coming into contact with the heated mold.

The mold cavities are provided with downwardly extending conicalcavities l9 and 20 for integrally casting the terminal posts on thestraps; Ejector pins 2? and 22 are shown at the base of thepost'cavities I9 and 20 for removing the completed element with attachedstrap-castings from the mold. The ejector pins may be actuated by anysuitable means not shown.

To provide for filling the mold, the gate cavities 23 and 24, located ingate blocks 25 and 26, are shown, through which the molten metal may bepoured into the mold cavities proper. The gate blocks are here shown asdetachable but may be integral with the mold block. After thecastingshave solidified, the gates may be cut off either after theelement and strap-castings have been removed from the mold or beforeremoval. In the latter case, the gate blocks 25 and 26 will first beremoved and the gates cut off in situ by any suitable means not shown.

Inserted through and closely fitting into suit- As shown in Fig. 2, theedges able openings in the floor of the mold cavities H and i2 are thesuper-heating inserts 21 and 28, respectively. Since these inserts arealike, the one shown at 21 will now be described. It comprises a blockof steel or similar heat-conducting refractory metal whose upperrectangular face is fiushwith the floor of the mold cavity II and islongitudinally substantially coextensive with that cavity. In width, itcorresponds with the horizontal length of the plate lugs I 6 and islocated immediately below the row of these positive plate lugs. Thevertical dimensions of the plate lugs I6 as here shown are such as tobring their ends close to but not actuallyin contact with the insert 21,leaving a narrqgv space 29 therebet-ween. Under some conditions,however, it may be satisfactory to bring these plate lugs into actualcontact with the insert. Except for a short distance from its uppersurface, the insert 21 is out of contact with the mold, there beinginterposed a Clearance space 30'to limit the transfer of heat from theinsert to the mold. 'J. 'he insert 21 is provided with a downwardlyextending projection 3| which is surrounded by a tubular water-cooledelectrical conducting call 32 adapted to carry high-frequencyalternating current for induc tively heating the insert 21 in thewell-known manner. Standard apparatus for developing and applyingsuitable high-frequency current for in ductive heating is available onthe market and it is not deemed necessary to illustrate or describe ithere.

The insert 21 is provided with a duct 33 through which cooling-liquidmay be circulated and suitably controlled as by the valve 34.

The operation of the apparatus above described is as follows:

The assembled element, comprising the desired number of positive andnegative plates with interposed separators clamped together in theirfinal relative positions, is inverted and supported on the mold as shownin Fig. 2, with the separators resting on the slab l8 and the plate lugsextending into the mold cavities ll and l2, with their ends above andclose to or in contact with the upper surfaces of the inserts 21 and 28,re-

spectively. Molten metal, preferably lead-anti mony alloy, is thenpoured into the mold cavities II and I2 via the gates 23 and 24 untilthe cavities are filled to the upper level including the spaces betweenand beneath the plate lugs. lhe temperature of the molten metal is suchthat the plate lugs will not be melted or softened but will retain theirshape or physical identity, as it has been found that such melting orsoftening produces crystallization and weakening of the lugs, causingthem to break when subjected to stress or vibration in service.- Theshrinkage of the molten metal on cooling and solidifying, which moltenmetal now around the plate lugs, as it rests in the mold, together withthe tips of the plate lugs are in a brief period of time raised to anelevated temperature to effect a. welding or fusing of the lugs to thestrap for only a short 'the lugs.

distance above the floor of the mold and without melting or fusing theroots or major portion of The heat necessary for the localized weldingor fusing of the lugs is applied through the super-heating inserts 21and 2B. In the illustrated form of the invention the shanks of theinserts are surrounded by high-frequency heating coils 32'.High-frequency current is passed through the heating coils 32 to heatinductively the inserts 21 and 28, the intensity and duration of thecurrent and the resultant temperature and rate of application of heat bythe inserts 21 and 28 to the metal being such as to melt the metal justabove the upper surfaces of the inserts and melt the tips of the platelugs. The intensity and duration of the current required to obtain thebest results will vary with the dimensions of the strap-casting and thesize and spacing of the plate lugs. With the volume of current availablefrom standard apparatus for inductive heating applied to a standard typeof storage battery element, a few seconds has been found adequate togive satisfactory results. As soon as the current is interrupted,cooling-water is circulated through the ducts in the inserts to preventfurther heating effect and also hastens the cooling, solidification andfinal shrinkage of the strap around the lug --roots.

The length of the mold cavities II and I2 may be made sufficient toprovide for the maximum width of element. For smaller elements, it isonly necessary to block off the ends of the mold cavities. No otheradjustment is necessary to provide for elements of various numbers orthickness of plates or various plate spacing.

It may be remarked that space is provided above the level of the moltenmetal in the mold and at the roots of the lugs for the access of air,which tends to keep the metal cool at the roots of the lugs and also tokeep the adjacent portions of t e separators cool.

It will be noted that there is provided, in accordance with thisinvention, a group of storage battery plates assembled by theirconducting lugs to a suitable connecting strap, wherein the plate lugsat their roots and over the major portion-of their length adjacent theplates are mechanically tightly gripped by the adjacent metal of thestrap without being autogenously welded thereto, while the tips of thelugs are autogenously welded to the adjacent metal of the strap.

While one convenient form of apparatus for carrying out the process andproducing the prodnot of this invention has been described, includinginductively heated means for applying the superheating temperaturelocally to the tips of the plate lugs and the adjacent metal of thestrap casting, it is not intended to limit the scope of the invention tothis particular apparatus since other means may be employed forapplyinglocalized superheating for the selective and localized fusing of theend-portions of the lugs to the adjacent metal of the strap.

This application is a division of my application Serial No. 538,564,filed June 3, 1944, and is-directed to and claims my improved processfor assembling storage battery elements described in my originalapplication. The described mold for the manufacture of storage batteriesis not claimed -herein'since it is the subject-matter of and is claimedin my original application Serial No, 538,564; nor is the describedproduct-claimed herein because it is the subject-matter of and isclaimed in my divisional application Serial No. 568,797, filed December19, 1944.

It will be obvious to those skilled in the art that modifications may bemade in details of construction and procedure without departing from thespirit of the invention which is not limited in respect to such mattersor otherwise than the appended claims may require.

1. claim:

1, in a process for casting straps on the plate lugs of an assembledstorage battery element comprising positive and negative plates andinterposed separators the steps of inverting the element and insertingthe plate lugs into a suitable mold, surrounding the lugs with moltenmetal at a temperature insuflicient to melt or soften the lugs, andafter the metal has cooled, while still in the mold applying heatlocally to the tips of the lugs and the surrounding metal in the moldfor a limited time suihcient to fuse them together only at said lugtips.

2, In a process for casting straps on the plate lugs of an assembledstorage batte y element comprisin positive and negative plates withinterposed separators the steps of inverting the element and insertingthe plate lugs into a suitable mold, surrounding the lugs with moltenmetal at a temperature such that when the metal comes into contact withthe lug-surfaces the metal is not hot enough to fuse such surfaces. andwhile the strap is still in the mold applying heat to a localized areaof the mold adjacent the tips of the lugs to effect localized fusing ofthe strap-metal to the ends of the lugs without fusing of the strapmetal to the roots of the lugs.

3. The method of producing on the lugs of storage battery plates a caststrap characterized by welded areas of high electrical conductivity atthe tip-ends of the lugs which comprises inserting the lugs of thestorage battery plates into a mold cavity with said lugs spaced fromeach other, surrounding the lugs with molten metal at a temperature suchthat when the metal comes into contact with the lug-surfaces the metalis not hot enough to fuse such surfaces, and while the strap is still inthe mold applying heat to a localized area of the mold adjacent the tipsof the lugs to effect localized fusing of the strap-metal to the 6 heatin a localized area of the mold adjacent the tips of the lugs to elevatethe temperature thereof during such a brief period of time as willeffect localized fusing of the strap-metal to the ends of the lugswithout fusing of the strap-metal to the roots of the lugs, andshrinking the metal around the roots of the lugs by removing heat fromthe localized area of the mold and from the metal.

5. The method of producing on the lugs of storage battery plates a caststrap characterized by welded areas of high electrical conductivity atthe tip-ends of the lugs which comprises inverting the plates andprojecting the lugs thereof downwardly into a mold cavity with said lugsspaced from each other, pouring into the mold and about the lugs moltenmetal at a temperature such that when the metal comes into contact withthe lugsurfaces the metal is not hot enough to fuse such surfaces and inquantity sumcient to form the strap, while the strap is still in themold applying heat to a localized area of the mold adjacent the tips ofthe lugs at a rate and during a time intercal ends of the lugs withoutfusing of the strap-metal metal to the ends of the lugs without fusingof the strap-metal to the roots of the lugs and thereafter cooling saidmetal.

6. The method of producing on the lugs of storage battery plates a caststrap characterized by welded areas of high electrical conductivity atthe tip-ends of the lugs and by shrinkage of the strap around the rootsof the lugs which comprises inverting the plates and projecting thelugsthereof downwardly into a mold cavity with said lugs spaced from eachother, pouring into the mold and about the lugs in quantity suflicientto form the strap molten metal at a temperature such that when the metalcomes into contact with the lug-surfaces the metal is not hot enough tofuse such surfaces, while the strap is still in the mold inductivelygenerating heat in a localized area of the mold adjacent the tips of thelugs at a rate and during a time interval which produces localizedfusing of the strap-metal to the ends of the lugs without fusing of thestrap-metal to the roots of the lugs. and shrinking the metal around theroots of the lugs by removing heat from said 10- ealized area of themold and from the metal.

CHARLES D. GALLOWAY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED e'rii'rne PATENTS Barhoif June 23, 19 31

